The invention refers to a device for granulating of material pressed out from at least one nozzle, in particular of thermoplastic synthetic material, comprising a perforated plate for the nozzle(s), to which a knife head carrying at least one knife is oppositely positioned, which knife head is connected to a shaft driven for rotation by a motor and is displaceable in its axial direction, so that each knife passes the nozzle mouth in contact therewith and thereby chops the granules, which are carried off the granulating housing surrounding the perforated plate by a cooling medium introduced into the granulating housing, wherein the motor is movable relative to the granulating housing suspended by means of a suspension, which movability, however, is only in the axial direction of the shaft, and wherein an adjustment means for the axial adjustment of the motor relative to the perforated plate is provided.
Granulating apparatus in which the shaft can be adjusted in an axial direction are known in a plurality of embodiments. Frequently, the shaft of the knife head is bearingly supported within a sleeve which can be axially shifted. Thereby, always the desired pressure can be adjusted by which the knives are pressed towards the perforated plate. Mostly, the torque is transferred to the knife shaft by means of a denture clutch. If water is used as the cooling medium for the chopped granules, as is mostly the case, the knife shaft must be tightened with respect to the housing. Within this, there result difficulties caused by friction. The axial displacement of the knife shaft causes also a displacement of the running surface of the sealing ring by which sealing against water is effected, so that the conditions of friction are continuously changing. In a similar manner, also the friction values of the denture clutch change when shifting the knife shaft. Further, it must be considered that the sleeve forming the bearing runs within a sliding bearing which must be lubricated. Also within this there occur friction values which change with time, because the lubricant (mostly oil) becomes more or less gummy after some time, so that a relatively high momentum for breaking away occurs which is in conflict with the requirement that as a rule only an unimportant axial friction is desired. Further, a sleeve bearing requires a certain effort.
Since the knife shaft must always be bearingly supported within the motor, it has already been proposed to replace the sleeve bearing by the motor bearing. This constructional variant, however, does not avoid the initially described difficulties.
A granulating apparatus of the initially described kind is known from DE 10302645 A1 in which the relative to the granulating housing movable suspension of the motor and therefore of the motor shaft is constituted by a rod-guide means extending in the axial direction of the motor shaft. Also such a construction does not avoid the mentioned difficulties of uncontrollable friction conditions.